Category: Research

New approach reveals ocean warming more than previously thought

New approach reveals ocean warming more than previously thought

By Georgina Wade

A study published in Nature suggests that oceans are warming far faster than the previous estimates laid out by the Intergovernmental Panel on Climate Change.

Using a new approach that derives ocean temperatures by measuring carbon dioxide and oxygen levels in the atmosphere, the study found that between 1991 and 2016 the oceans warmed an average of 60 percent more per year than the panel’s official estimates.

If proven accurate, the new temperature estimates could be an indication that global warming has exceeded conservative estimates and is more in line with predicted worst-case scenarios.

Led by Laure Resplandy, a biogeochemical oceanographer at Princeton University, the research finds that the IPCC’s measurements for observed ocean heat were too low.

“Their estimates overlap with previous estimates, but it’s aligned with some of the higher estimates,” she said.  “It’s not like completely changing our understanding of what the ocean might be taking up – it’s a new type of measurement that’s weighing in toward the higher end of that.”

Although her work differs from IPCC findings, Resplandy emphasised that her findings do not oppose the IPCC’s dire warning of only 12 years to limit climate change catastrophe, “it doesn’t change the results,” she said. “What it does is that it makes it harder to get there.”

Recent problems found regarding calculations made in the study do not invalidate the study’s methodology. In a note added to the original news release, co-author Ralph Kneeling wrote:

 “I am working with my co-authors to address two problems that came to our attention since publication. These problems, related to incorrectly treating systematic errors in the O2 measurements and the use of a constant land O2:C exchange ratio of 1.1, do not invalidate the study’s methodology or the new insights into ocean biogeochemistry on which it is based. We expect the combined effect of these two corrections to have a small impact on our calculations of overall heat uptake, but with larger margins of error.  We are redoing the calculations and preparing author corrections for submission to Nature.”


Cover photo by Victor Carvalho on Unsplash
Parts of the world could be facing multiple climate-related crises at once by 2100

Parts of the world could be facing multiple climate-related crises at once by 2100

By Elisa Jiménez Alonso

A newly published study in Nature Climate Change finds that risks posed by climate change will be so wide-ranging by the end of this century that some parts of the world could face up to six climate-related crises simultaneously.

The paper analyses a range of climate hazards including heatwaves, wildfires, sea level rise, hurricanes, flooding, drought and water shortages. Many of these problems are already being noticed around the world. This year alone several severe flood events occurred around the world from Japan and Nigeria to the United States, in summer a heatwave led to temperature records across the whole Northern Hemisphere. Just last week, California experienced some of its worst wildfires in its history.

According to the paper, under current greenhouse gas emission scenarios, the situation will get much worse. By 2100, large parts of the world, especially in the Tropics and mostly coastal areas, might experience up to 6 simultaneous climate-related crises. Lead author of the study Camilo Mora, University of Hawaii, described the prospect “like a terror movie that is real.”

Global map of cumulative climate hazards. The main map shows the cumulative index of climate hazards, which is the summation of the rescaled change in all hazards between 1955 and 2095. Smaller maps indicate the difference for each individual hazard for the same time period. Individual hazards were rescaled to be normalized between − 1 and 1. Negative values indicate a decrease in the given hazard, whereas positive values represent an increase relative to the 1950s baseline values. The largest value in the cumulative index was six (that is, cumulatively, the equivalent to the largest change in six climate hazards occurred for any one cell). Plots are based on RCP 8.5, results for all three mitigation scenarios are provided in Supplementary Figs. 1–3. An interactive data visualization is available at https://maps.esri.com/MoraLab/CumulativeChange/index.html and time-series animations at http://impactsofclimatechange.info/HumanImpacts/HeatWaves_rcp26.html.

According to the authors the largest losses of human life during extreme climate events will occur in developing nations, while developed nations will mostly be impacted by high economic losses, a trend that is already true today. To accompany the paper, ESRI developed an interactive map to visualize the findings of the study and even under the most optimistic emission scenario it is clear that adaptation and resilience building are a dire necessity pretty much all over the globe. “We see that climate change is literally redrawing the lines on the map and revealing the threats that our world faces at every level,” said Dawn Wright, ESRIS’s chief scientist.

The paper includes a multidisciplinary effort by 23 authors who reviewed over 3,000 papers on the effects of climate change determining close to 500 ways in which these effects could impact human physical and mental health, food security, water availability, infrastructure and many other aspects.

This study is just another urgent reminder that inaction in terms of climate change mitigation and also adaptation will come at way too high a cost, not just economically but also in terms of human lives.


Mora, C., Spirandelli, D., Franklin, E., Lynham, J., Kantar, M., Miles, W., Smith, C., Freel, K., Moy, J., Louis, L., Barba, E., Bettinger, K., Frazier, A., Colburn IX, J., Hanasaki, N., Hawkins, E., Hirabayashi, Y., Knorr, W., Little, C., Emanuel, K., Sheffield, J., Patz, J. and Hunter, C. (2018). Broad threat to humanity from cumulative climate hazards intensified by greenhouse gas emissions. Nature Climate Change. Access the article by clicking here (paywall).

Cover photo by Eoghan Rice – Trócaire / Caritas (CC BY 2.0): Debris lines the streets of Tacloban, Leyte island. This region was the worst affected by typhoon Hayan in 2013, causing widespread damage and loss of life.
Ocean warming may be faster than thought

Ocean warming may be faster than thought

By Tim Radford

Science knows that ocean warming is occurring. A big challenge now is to work out how quickly the temperature is rising.

The seas are getting hotter – and researchers have thought again about just how much faster ocean warming is happening. They believe that in the last 25 years the oceans have absorbed at least 60% more heat than previous global estimates by the UN’s Intergovernmental Panel on Climate Change (IPCC) had considered.

And they calculate this heat as the equivalent to 150 times the annual human electricity generation in any one year.

“Imagine if the ocean was only 30 feet (10m) deep,” said Laure Resplandy, a researcher at the Princeton Environment Institute in the US. “Our data show that it would have warmed by 6.5°C every decade since 1991. In comparison, the estimate of the last IPCC assessment report would correspond to a warming of only 4°C every decade.”

The oceans cover 70% of the Blue Planet, but take up about 90% of all the excess energy produced as the Earth warms. If scientists can put a precise figure to this energy, then they can make more precise guesses about the surface warming to come, as humans continue to burn fossil fuels, release greenhouse gases such as carbon dioxide into the atmosphere, and drive up the planetary thermometer.

“There will have to be an even more drastic shutdown of fossil fuel investment and an even faster switch to renewable sources of energy”

At the academic level, this is the search for a factor known to climate researchers as climate sensitivity: the way the world responds to ever-increasing ratios of greenhouse gas in the atmosphere.

At the human level, this plays out as ever-greater extremes of heat, drought and rainfall, with ever-higher risks of catastrophic storm or flood, or harvest failure, and ever-higher tallies of human suffering.

Comprehensive global measurements of ocean temperature date only from 2007 and the network of robot sensors that deliver continuous data about the top half of the ocean basins.

Dr Resplandy and her colleagues report in the journal Nature that they used a sophisticated approach based on very high-precision measurements of levels of oxygen and carbon dioxide in the air.

Gases released

Both gases are soluble, and the oceans are becoming more acidic as the seas absorb ever-greater levels of carbon dioxide. But as seas warm, they also become less able to hold their dissolved gases, and release them into the atmosphere.

This simple consequence of atmospheric physics meant that the researchers could use what they call “atmospheric potential oxygen” to arrive at a new way of measuring the heat the oceans must have absorbed over time.

They used the standard unit of energy: the joule. Their new budget for heat absorbed each year between 1991 and 2016 is 13 zettajoules. That is a digit followed by 21 zeroes, the kind of magnitude astronomers tend to use.

That the oceans are warming is no surprise: this has been obvious from the crudest comparison of old naval data with modern surface checks, and for years some researchers argued that ever-higher ocean temperatures could account for the so-called slowdown in global warming in the first dozen years of this century.

Challenging achievement

The new finding counts first as an academic achievement: there is now a more precise thermometer reading, and new calculations can begin.

One of the researchers, Ralph Keeling of the Scripps Institution of Oceanography, said: “The result significantly increases the confidence we can place in estimates of ocean warming and therefore help reduce uncertainty in the climate sensitivity, particularly closing off the possibility of very low climate sensitivity.”

But the result also suggests that internationally agreed attempts to hold planetary warming to a maximum of just 2°C – and the world has already warmed by around 1°C in the last century – become more challenging.

It means that there will have to be an even more drastic shutdown of fossil fuel investment and an even faster switch to renewable sources of energy such as sun and wind power.


Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.

This article was originally published on Climate News Network.

Cover photo by Giga Khurtsilava on Unsplash
Wildfires in Mediterranean Europe will increase by 40% at 1.5°C warming, say scientists

Wildfires in Mediterranean Europe will increase by 40% at 1.5°C warming, say scientists

By Cristina Santin,Swansea University and Stefan H Doerr, Swansea University

Europe’s Mediterranean regions have strong sunshine, bright blue seas, beautiful beaches, and pretty holiday houses immersed in pine forests that provide welcome shade. It sounds very inviting, but such a scenario is also perfect for severe wildfires such as the ones that killed 99 people this July in the popular holiday resort of Mati, in Greece.

Now, new research in Nature Communications suggests that the summer fire season in Mediterranean Europe is going to get worse. Under the hottest climatic predictions of 3°C warming, the area that is currently burned every year would double. Even more worryingly, 40% more area would be burnt even if the Paris Climate Agreement is fulfilled and warming stays below “only” 1.5°C.

So, time for Europeans to start looking for other holiday destinations? Hang on. Let´s look at the new study in more depth first.

In this modelling exercise, a team of scientists led by Marco Turco, a fire researcher at the University of Barcelona, predict the area that would burn in future summers in Mediterranean Europe following different degrees of warming. They base their approach on the findings of a recent study from some of the same authors, which looked at Portugal, Spain, southern France, Italy and Greece, and established a direct association between the area burnt in the summer months and summer drought in recent decades (1985-2011). They use that “fire-drought” relationship to estimate the area burnt under the drought conditions forecasted in three different warming scenarios (1.5°C, 2°C and 3°C).

The climate obviously has a direct effect on fires, as hotter conditions lead to drier vegetation more susceptible to burning. But the authors also account for indirect effects such as drier conditions reducing plant growth, meaning there is less vegetation to “fuel” the fires. This “non-stationary” climate-fire modelling is important because if the indirect effects were not considered the predictions of area burnt would be even higher.

So, are Turco and co-authors right? Will the future look blacker for the Mediterranean? Will tragic events, like those in Mati, become more frequent? Turco’s predictions, even if in many ways the most advanced to date, still carry a huge uncertainty, but they add to the growing list of studies that forecast more Mediterranean fire activity in future.

Climate change is not the only factor

What their study is unable to predict is the influence of perhaps the most important factor behind the future occurrence of fires, also the very same factor that is responsible for accelerated climate warming: humans.

Humans are the main source of ignition in most of the Mediterranean, and the main modifiers of vegetation cover. Including them (or us) in scientific models of fire is very challenging, and can radically change the results. For example, at the global scale, models that rely on climate change tend to predict a very substantial increase in area burnt – a hotter world means more fires, as you’d expect. But when human effects are incorporated, the estimated total area burnt can actually decrease to levels even below current ones. This is essentially because more and more land worldwide is being urbanised or converted to agriculture, resulting in smaller and more fragmented “wildland” areas that can burn.

We still have plenty to worry about, however, as global averages form only a small part of the story. In some parts of the world, such as Canada and the US, the area burned is already on the increase. Meanwhile, some houses are being built further into forests and other flammable vegetation, while other houses are finding themselves now surrounded by vegetation as nearby fields are abandoned and left to nature. Both situations leave more people exposed to fires.

In Mediterranean Europe the situation is particularly complex as the ongoing abandonment of traditional land uses is changing the vegetation more dramatically than climate change. Intensely grazed or cultivated land is becoming overgrown with shrubs or replaced with fire-prone forest stands, a trend that makes the landscape more flammable. This, combined with climate warming, can provide the perfect recipe for fire disasters. For example, Greece has seen less than half the area burned so far this summer than the 2008-17 average), but lots of dry vegetation for fuel, strong winds and a high population density combined to cause Greece’s deadliest fire on record.

The future of fire in Mediterranean Europe ultimately depends on the decisions we make. That means complying with the Paris Climate Agreement to reduce global warming but also adapting effectively to the increased risk of fire. And this does not necessarily mean suppressing all fires, which is often not possible, but managing the fuel and how we live among it. Policies aimed at removing fire completely from the landscape have long proven to fail, even if many countries still follow them.

Instead we need to create fire-resilient landscapes and fire-resilient societies. A holiday house in the middle of a pine forest may sound idyllic, but it can be a death trap when a fire occurs, and the study by Turco and his co-authors suggests that this will be even more likely in the future.The Conversation


Cristina Santin, Sêr Cymru II Fellow & Senior Lecturer, Geography & Biosciences Departments, Swansea University and Stefan H Doerr, Professor of Geography and Editor in Chief of the International Journal of Wildland Fire, Swansea University. This article is republished from The Conversation under a Creative Commons license. Read the original article.

Cover photo by Michael Held on Unsplash

The Conversation

USA among top countries to suffer highest economic damage due to climate change according to new research

USA among top countries to suffer highest economic damage due to climate change according to new research

A recently published study indicates climate change is costing the USA hundreds of billions of dollars per year.

The results, which were published in Nature Climate Change, use climate model projections, empirical climate-driven economic damage estimations and socioeconomic forecasts to estimate country-level contributions to the social cost of carbon (SCC). SCC is an estimate that adds up “all the quantifiable costs and benefits of emitting one additional tonne of CO2, in monetary terms” and is used to weigh the benefits of reducing global warming against the costs of cutting greenhouse gas emissions.

The study shows the global SCC is significantly higher than that used by the US American government to inform policy decisions. The latest numbers from the U.S. Environmental Protection Agency (EPA) for global costs range from US$12 to US$62 per metric tonne of CO2 emitted by 2020. However, the new data shows the SCC to be as high as US$180–800 per tonne of carbon emissions.

The country-level SCC for the USA alone is estimated to be US$50 per tonne, which is much higher than the global value used in most regulatory impact analyses. This means that the nearly five billion metric tons of CO2 the USA emits each year is costing the US economy about US$250 billion.

“Evaluating the economic cost associated with climate is valuable on a number of fronts, as these estimates are used to inform U.S. environmental regulation and rulemakings,” said lead author, University of California San Diego assistant professor Kate Ricke, who holds joint appointments with UC San Diego’s School of Global Policy and Strategy and Scripps Institution of Oceanography.

CO2 is a global pollutant and previous analyses have always focused on the global SCC, but this paper offers a country-by-country breakdown of the economic damage climate change will cause.

“Our analysis demonstrates that the argument that the primary beneficiaries of reductions in carbon dioxide emissions would be other countries is a total myth,” Ricke said.  “We consistently find, through hundreds of uncertainty scenarios, that the U.S. always has one of the highest country-level SCCs. It makes a lot of sense because the larger your economy is, the more you have to lose. Still, it’s surprising just how consistently the US is one of the biggest losers, even when compared to other large economies.”


Ricke, K., Drouet, L., Caldeira, K. and Tavoni, M. (2018). Country-level social cost of carbon. Nature Climate Change. Available here https://www.nature.com/articles/s41558-018-0282-y. [paywall]

Cover photo by Antonio DiCaterina on Unsplash
First ever assessment of climate change influence on India’s hydropower plants points to increased generation potential

First ever assessment of climate change influence on India’s hydropower plants points to increased generation potential

Will Bugler

Climate change will have a significant impact on India’s hydropower plants, according to a new study. Changes in rainfall patterns, snowmelt and streamflow in India’s major rivers however, will affect the design and operation of India’s planned and current hydro plants. Amazingly however, the role of climate change on hydroelectric facilities in the country remains largely unexplored.

India is the world’s 7th largest producer of hydropower, and the predictable, low-carbon energy source is vitally important for the country’s ambitions to improve energy supplies and cut greenhouse gas emissions. With India’s population continuing to grow, the demand for clean energy will rise in the coming years. Hydropower offers considerable potential to meet some of this demand. Estimates suggest that the country uses less than 20 % of its total hydropower potential.

Dams must be built to last

As with other large infrastructure developments, proper consideration of climate change on hydroelectric facilities is essential. The lifespan of a large, concrete dam can extend to well over 100 years. A hydropower dam built today will be operational in a considerably different climate in its later life.

The study, undertaken by researchers from the Indian Institute of Technology, provides the first-ever assessment of climate change impacts on the hydropower potential of 7 large hydropower projects in India. Each facility has an installed capacity of over 300 MW, and most are among the top 10 largest hydropower projects in the country.

The study found that all 7 reservoirs studied are projected to experience greater levels of overall rainfall by the end of the century, with some being up to 18% wetter than today. However, the increase in rainfall will not be evenly spread throughout the year. The authors expect that much of the increase will fall as heavy, monsoon rains. This means that the hydro-electric dams may have to withstand more severe flood events than have been previously experienced. It also means that streamflow will not increase throughout the year, meaning that the increased rainfall is unlikely to be matched by a similar increase in electricity generation potential.

The study also found that snow cover is likely to decline affecting several catchments of hydroelectric facilities. This decline in snow cover will mean reduce its contribution to streamflow in the winter season.

Other factors affect streamflow

Overall, the study found that that there would be an increase in streamflow for the 7 hydropower facilities, and that with good planning, India could increase its overall generation from hydropower. Planners should take account of climate-driven changes in streamflow to best capitalise on these changes.

To do this, it will be important to consider other factors, notably the changing demand for irrigation. Increased irrigation demand can have a significant effect on streamflow and reduce hydropower production capacity. If rain falls over shorter periods of time and in more intense bursts, the demand for irrigation in the longer dry periods is likely to rise. This could offset some of the potential increase in generation.

Other factors such as changing land-use patterns will also have significant impacts on India’s hydropower production capacity. However, it is clear from this study that climate change will have significant influence on the streamflow that reaches each facility. As streamflow is highly localised, and dependent of many contributing factors relating to local geography, assessments should be carried out on all current and proposed hydropower plants to assess how they will operate under various climate scenarios.

The study Projected Increase in Hydropower Production in India under Climate Change can be found here.


Kumar, A., Kumar, K., Kaushik, N., Sharma, S. & Mishra, S. Renewable energy in India: Current status and future potentials. Renew. Sustain. Energy Rev. 14, 2434–2442 (2010).

Cover photo by Thangaraj Kumaravel/Flickr (CC BY 2.0): Sharavathi hydroelectric power plant view.
Filipino farmers advised to adapt to erratic rain

Filipino farmers advised to adapt to erratic rain

By Paul Icamina

[MANILA] Rainfall patterns are changing so much that farming schedules in the Philippines may no longer hold true, a public awareness campaign this month (August) heard.

Timely rainfall is considered vital for the growth and production of food crops. With the world’s climate changing, temperatures are influencing rainfall so that it is in excess in some areas and deficient in others, upsetting traditional farming cycles. Warming is also causing sea-level to rise and turn soils in coastal areas saline.

“We can no longer rely on traditional farming knowledge and practices”

– Anthony Payonga, Bicol University Graduate School

“The weather is no longer stable,” said Anthony Payonga, dean, Bicol University Graduate School, during the 8—10 August campaign organised by the Department of Science and Technology. “This has deep implications for Philippine agriculture.”

The changing trends were observed three years ago using rain gauges and validated by interviews and historical climate records. “Previously, the rainfall pattern was the same in areas extending 50—100 square kilometres, but now rainfall patterns are different in areas barely 3—4 kilometres away from each other.”

Payonga is lead researcher of the Bicol Agri-Water Project (BAWP), a five-year initiative to increase the knowledge and skills of farmers to adapt to climate change and improve harvests in the watersheds in Camarines Sur and Albay provinces.

“Cropping patterns must change and not just for rice but also for other crops. We can no longer rely on traditional farming knowledge and practices, but farmers continue to plant rice varieties that are susceptible to flooding during the June—July rainy season,” Payonga said.

“Farmers will now know what to do during flood and drought conditions,” says Marissa Estrella, director of the Bicol Consortium for Agriculture and Resources Research and Development, a BAWP research partner. “It brings complicated science down to the level of farmers’ understanding.”

The Bicol region is self-sufficient in rice, contributing seven per cent to national production. However, average yields declined from 3.41 metric tonnes per hectare in 2010 to 3.3 metric tonnes per hectare in 2011 due to “climatic aberrations”.

BAWP developed packages that included the production and distribution of rice varieties meant for areas prone to flooding, drought and salt intrusion, the latter when sea levels rise due to climate change. Buffer stocks now ensure access to quality seeds after extreme weather conditions.

Farmers get timely climate and weather information and provisions have been made for early warning systems, for example against pest infestations. The planting of alternative food crops such as white corn, cassava, sweet potato, banana and root crops is encouraged.

BAWP also set up climate field schools to train farmers. Bayani Abarquez, a farmer in Polangui, Albay province, who attended one of the schools, doubled harvests by using hybrid rice varieties and cropping and hazard calendars. He alternates chemical fertilisers with natural fertilisers and soil conditioners and uses fermented juices of chili, neem and madre de cacao against farm pests.


This piece was produced by SciDev.Net’s Asia & Pacific desk. This article was originally published on SciDev.Net and is shared under a Creative Commons license (CC BY 2.0). Read the original article.

Cover photo by IRRI/Wikimedia Commons (CC BY 2.0): Filipino rice farmers in Laguna province incorporate rice straw, a good and abundant source of organic material, back in the field.

Hothouse Earth: here’s what the science actually does – and doesn’t – say

Hothouse Earth: here’s what the science actually does – and doesn’t – say

Editor’s note: Almost two weeks ago we published an article about the “Hothouse Earth” study. Today we share this piece by Richard Betts (Met Office, University of Exeter) to offer additional information about the findings of the study and the science behind it.

By Richard Betts, University of Exeter

A new scientific paper proposing a scenario of unstoppable climate change has gone viral, thanks to its evocative description of a “Hothouse Earth”. Much of the media coverage suggests that we face an imminent and unavoidable extreme climate catastrophe. But as a climate scientist who has carried out similar research myself, I am aware that this latest work is a lot more nuanced than the headlines imply. So what does the hothouse paper actually say, and how did the authors draw their conclusions?

First, it’s important to note that the paper is a “perspective” piece – an essay based on knowledge of the scientific literature, rather than new modelling or data analysis. Leading Earth System scientist Will Steffen and his 15 co-authors draw on a diverse set of literature to paint a picture of how a chain of self-reinforcing changes might potentially be initiated, eventually leading to very large climate warming and sea level rise.

One example would be the thawing of Arctic permafrost, which releases methane into the atmosphere. As methane is a greenhouse gas, this means the Earth retains more heat, causing more permafrost to thaw, and so on. Other possible self-reinforcing processes include the large-scale die-back of forests, the melting of sea ice, or the loss of ice sheets on land.

Global map of potential tipping cascades, with arrows showing potential interactions. Steffen et al (2018) / PNAS

Hothouse or stabilised?

Steffen and colleagues introduce the term “Hothouse Earth” to emphasise that these extreme conditions would be outside those that have occurred over the past few hundred thousand years, which have been cycles of ice ages with milder periods in between. They also present an alternative scenario of a “Stabilised Earth” where these changes are not triggered, and the climate remains similar to now.

The authors make the case that there is a level of global warming which is a critical threshold between these two scenarios. Beyond this point, the Earth System might conceivably become set on a pathway that makes the extreme “hothouse” conditions inevitable in the long term. They argue – or perhaps speculate – that the process of irreversible self-reinforcing changes could in theory start at levels of global warming as low as 2°C above pre-industrial levels, which could be reached around the middle of this century (we are already at around 1°C). They also acknowledge large uncertainty in this estimate, and say that it represents a “risk averse approach”.

A key point is that, even if the self-perpetuating changes do begin within a few decades, the process would take a long time to fully kick in – centuries or millennia.

Steffen and colleagues support their suggestion of a threshold at 2°C through reference to previously-published scientific work. These include other review papers which themselves drew on wider literature, and an “expert elicitation” study in which scientists were asked to estimate the levels of global warming at which “tipping points” for these key climate processes might be passed (I was one of those consulted).

The authors argue that 2°C can still be avoided if humanity takes concerted action to reduce its warming effect on the climate. In a similar way that the “Hothouse Earth” scenario involves huge changes in the climate system with multiple effects of one process leading to another, the concerted global action to avoid 2°C would, they suggest, also involve huge changes in the human system, again with several fundamental steps leading from one change to another.

Don’t ignore the caveats

Personally, I found this an interesting and important think piece that was well worth reading. But since this is not actually new research, why is it getting so much coverage? I suspect that one reason is the use of the vivid “Hothouse Earth” term at a time when everyone’s talking about heatwaves. Another is that it’s clearly a dramatic narrative, and not surprisingly this has led to some sensationalist articles.

With some exceptions, much of the highest-profile coverage of the essay presents the scenario as definite and imminent. The impression is given that 2°C is a definite “point of no return”, and that beyond that the “hothouse” scenario will rapidly arrive. Many articles ignore the caveats that the 2°C threshold is extremely uncertain, and that even if it were correct, the extreme conditions would not occur for centuries or millennia.

Some articles do however emphasise the more tentative nature of the work, and some push back against this overselling of the doomsday scenario, arguing that provoking fear or despair is counterproductive.

One thing that strikes me about the scientific literature on “tipping points” is that there are a lot of review papers like this that end up citing the same studies and each other – indeed, my colleagues and I wrote one a while ago. There is a great deal of interesting, insightful research going on using theoretical methods and calculations with large approximations. However, we have yet to see an equivalent level of research in the highly-complex Earth System Models which generate the kind of detailed climate projections used for addressing policy-relevant questions by the Intergovernmental Panel on Climate Change (IPCC).

The ConversationSteffen and colleagues have made a good start at addressing such questions, going as far as they can on the basis of the existing literature, but their essay should motivate new research to help narrow down the huge uncertainties. This will help us see better whether “Hothouse Earth” is our destiny, or mere speculation. In the meantime, awareness of the risks – however tentative – can still help us decide how to manage our impact on the global climate.


Richard Betts, Met Office Fellow and Professor of Climate Impacts, University of Exeter. This article was originally published on The Conversation. Read the original article.

Photo by Hasan Almasi on Unsplash.
2018-2022 likely to be abnormally warm

2018-2022 likely to be abnormally warm

By Elisa Jiménez Alonso

A new study published in Nature Communications finds that from 2018 until 2022 the world is likely to experience a warmer than normal period, temporarily reinforcing the long-term global warming trend and bringing an increased likelihood of intense to extreme temperatures.

The past years were the warmest on record and after a scorching summer on the Northern Hemisphere, it seems there might be little respite in the coming four years. Natural variation in the climate system will amplify the effects of rising greenhouse gas emissions and lead to a warmer than normal period.

In the study, researchers fed data from ten existing climate models from the Coupled Model Intercomparison Project phase 5 (CMIP5) into their probabilistic model to project how natural variability and global warming could play together in the coming five years. The results show a 58% probability that, globally, the temperatures from 2018 until 2022 will be abnormally warm, and a 69% chance that oceans will be too.

The scientists emphasise that these results do not provide predictions about heatwaves, wildfires, Arctic ice melt, or droughts. Such events might be more likely but the model is global and does not predict anything specific about regional impacts or seasonal anomalies.

“Natural variability is a wriggle around the freight train that is global warming,” author of the paper, Florian Sévellec of the French National Centre for Scientific Research says. “On a human scale, it is what we feel. What we don’t always feel is global warming. As a scientist, this is frightening because we don’t consider it enough. All we can do it give people information and let them make up their own mind.”

The coming years will undoubtedly test this forecast, but as Dr Sam Dean, chief climate scientist at New Zealand’s National Institute of Water and Atmospheric Research says, “while we can’t be sure exactly how things will play out, at the moment the odds are higher for hot years.”

Climate trends in the past years and also this year have shown that things are changing and preparing for climate impacts remains a priority around the world.


 Sévellec, F., & Drijfhout, S. S. (2018). A novel probabilistic forecast system predicting anomalously warm 2018-2022 reinforcing the long-term global warming trend. Nature Communications, 9(1), 3024. https://doi.org/10.1038/s41467-018-05442-8

Cover photo by RonPorter/Pixabay (public domain)
‘Hothouse Earth’: New study finds Earth could enter an even hotter new normal

‘Hothouse Earth’: New study finds Earth could enter an even hotter new normal

By Elisa Jiménez Alonso

A new study published in Proceedings of the National Academy of Sciences (PNAS) shows that Earth could enter what the authors call ‘Hothouse Earth’ conditions where the average global climate could stabilise at 4-5°C above pre-industrial temperatures and sea levels could rise 10-60 m higher than today.

Mitigation alone won’t be enough for ‘Stabilized Earth’

The study, which has received wide-spread attention, also shows that keeping global warming within 1.5-2°C – a state the authors call ‘Stabilized Earth’ – may be a more daunting task than previously thought. It would not only require a significant reduction of greenhouse gas emissions but also enhancing or creating new carbon sinks, efforts to actively remove CO2 from the atmosphere, possibly solar radiation management, and adaptation to climate change impacts that are already happening and unavoidable.

“Human emissions of greenhouse gas are not the sole determinant of temperature on Earth. Our study suggests that human-induced global warming of 2°C may trigger other Earth system processes, often called ‘feedbacks’, that can drive further warming – even if we stop emitting greenhouse gases,” says lead author Will Steffen from the Australian National University and Stockholm Resilience Centre.

Health, economies, and political stability at risk

‘Hothouse Earth’ could potentially be uncontrollable and dangerous to most of Earth’s population, especially if the transition happens within only a century or two, which, following current pathways, wouldn’t be unlikely according to the scientists. This in turn would have fatal effects on health, economy, and political stability, but could also make portions of the planet uninhabitable for humans.

The study shows that agricultural production and water supplies are especially vulnerable to severe climate changes, leading to hot/dry or cool/wet extremes. These, obviously, would have severe impacts on society. The authors say “societal declines, collapses, migrations/resettlements, reorganizations, and cultural changes were often associated with severe regional droughts and with the global megadrought at 4.2–3.9 thousand years before present, all occurring within the relative stability of the narrow global Holocene temperature range of approximately ±1 °C.”

A growing need for building climate resilience

As highlighted in the study, even if a ‘Stabilized Earth’ state is achieved, Earth will be warmer than “at any other time in which fully modern humans have existed.” It would also still lead to the activation of some tipping elements and radical shifts in the ecosystems that support human life. The researchers state that current development strategies focused on economy efficiency will not be able to cope with these trends.

Global map of potential tipping cascades. The individual tipping elements are color- coded according to estimated thresholds in global average surface temperature (tipping points). Arrows show the potential interactions among the tipping elements based on expert elicitation that could generate cascades. Note that, although the risk for tipping (loss of) the East Antarctic Ice Sheet is proposed at >5 °C, some marine-based sectors in East Antarctica may be vulnerable at lower temperatures.

The emphasis now should clearly be on strategies that have the potential to transform human systems and make them climate resilient. Speaking in broad terms, the authors point out five characteristics climate resilience strategies should have:

  1. Maintenance of diversity, modularity, and redundancy;
  2. management of connectivity, openness, slow variables, and feedbacks;
  3. understanding social–ecological systems as complex adaptive systems, especially at the level of the Earth System as a whole;
  4. encouraging learning and experimentation; and
  5. broadening of participation and building of trust to promote polycentric governance systems.

Additionally, the authors of the study emphasise that their initial analysis would need to be underpinned by further research and Earth System analysis and modeling studies to address three critical questions:

  1. Is humanity at risk for pushing the system across a planetary threshold and irreversibly down a Hothouse Earth pathway?
  2. What other pathways might be possible in the complex stability landscape of the Earth System, and what risks might they entail?
  3. What planetary stewardship strategies are required to maintain the Earth System in a manageable Stabilized Earth state?

Steffen, W., Rockström, J., Richardson, K., Lenton, T.M., Folke, C., Liverman, D., Summerhayes, C.P., Barnosky, A.D, Cornell, S.E., Crucifix, M., Donges, J.F., Fetzer, I., Lade, S.J., Scheffer, M., Winkelmann, R., and Schellnhuber, H.J. (2018) Trajectories of the Earth System in the Anthropocene. Proceedings of the National Academy of Sciences (USA), DOI: 10.1073/pnas.1810141115

Cover photo by Siddharth Kothari on Unsplash